I am a TS16949 certified auditor. One of the qualifications listed in the current application was to be an AIAG certified QS9000 auditor. I am quite sure that most, if not all, TS auditors are QS auditors. Anyone, can become a QS auditor by being an ISO auditor, being observed and evaluated by Plexus proctors on your auditing skills, passing a written examination covering ISO, QS, PPAP,
APQP,
FMEA, MSA and SPC reguirements (closed book for the test questions, open book for the auditing questions, allowing up to 5 hours for completion), and having 3 years of relevant automotive experience. Once you become a QS auditor you can upgrade to a TS auditor by taking the PLEXUS 2 day TS training, auditor observation, a 3 hour test on all of the above plus the TS requirements, and a 10 minute oral review board.
The intent of the IATF/IAOB is to control the quality and knowledge base of the QS/TS auditors and to make sure they are qualified to audit automotive systems. They state that "Just because you can pass the written examination does not mean that you know how to properly complete an APQP package, a FMEA, a control plan etc, and audit an automotive quality system".